The sighting of a recently hatched condor chick in a nest cave deep in the Grand Canyon has boosted to 77 the flock of endangered giant scavengers in northern Arizona.

The Arizona flock has produced at least three fledglings this year — and a total of 18 since the reintroduction project started in 1996.

The first two chicks hatched this year were spotted by proud biologists in cliff-face nests in the Vermillion Cliffs, just north of the Grand Canyon.

Despite a decade of effort and millions of dollars spent, the massive birds with their nine-foot wingspans remain perched on the edge of trouble, mostly because of the lead bullet fragments in the bodies of the hunter-killed deer, elk and other game animals on which the condors feed. Even lead fragments the size of a grain of salt can cause digestive and other problems when the birds feed on the carcass. Experts note that those same fragments can contaminate the meat hunters bring home from their kills.

Lead bullet fragments have killed at least 23 condors since 2000, prompting the Arizona Game and Fish Department to appeal to hunters to use non-lead bullets and shotgun pellets in the vast area across which the condors roam. Game and Fish reports that 90 percent of the hunters in the area have now heeded those pleas and switched to non-toxic ammunition.

The condors have remained centered on the Vermillion Cliffs, where each year the Peregrine Fund releases more condors raised in captivity. The captive-reared birds are taught to avoid humans and power lines then released into flocks in California, Arizona and northern Mexico.

Visitors often see the condors at the Navajo Bridge near Lees Ferry. Other birds frequently visit the South Rim of the Grand Canyon, drawn apparently by all the activity along the rim. Birds from the Arizona flock have also shown up at Bryce and Zion national parks in Utah.

The giant scavengers that fed on camels, ground sloths and other giant, Ice Age creatures had dwindled to a handful of birds in California when biologists captured the last few survivors to start a captive breeding program.

The Peregrine Fund manages the effort now, under the terms of contracts with the U.S. Fish and Wildlife Service, Arizona Game and Fish and the U.S. Bureau of Land Management.

The latest addition to the condor flock showed up at the entrance to a cave in the Grand Canyon where his parents had built a nest. Biologists had been watching the cave for weeks, hoping for some sign that the pair had produced a chick.

The first condor chick produced in the wild was also born in a cave in the Grand Canyon. When biologists entered the cave to check on the chick, they found condor bones dating back 10,000 years to the Ice Age, when the giant birds had last used the nest site.